The starry disk that is our galaxy may extend
at least 50 percent farther from its apparent
edge than we thought. Instead of being
flat, the Milky Way appears grooved like a vinyl
record, upping its width to at least 150,000
light-years, researchers now say.
In 2002 and 2004, astronomers found two
rings of stars, Monoceros and Triangulum
Andromeda, beyond the disk’s known edge. But
this new study, published in The Astrophysical
Journal in March, suggests that what looked like the
disk’s edge is just a deep groove, and the two apparent
stellar rings are actually part of the disk.
Study co-author Heidi Jo Newberg of Rensselaer Polytechnic Institute
in Troy, N.Y., and colleagues believe the grooves might be caused by one or more
small galaxies, or galaxy-size nuggets of dark matter, being gravitationally dunked
into the Milky Way, like stones thrown into water.
[This article originally appeared in print as "Galactic Gains."]